98 lines
2.1 KiB
JavaScript
98 lines
2.1 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2020 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isnan = require( '@stdlib/math/base/assert/is-nan' );
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var isPositiveZero = require( '@stdlib/math/base/assert/is-positive-zero' );
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// MAIN //
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/**
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* Calculates the maximum value of a strided array via a callback function.
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*
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* @param {PositiveInteger} N - number of indexed elements
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* @param {Collection} x - input array/collection
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* @param {integer} stride - index increment
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* @param {NonNegativeInteger} offset - starting index
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* @param {Callback} clbk - callback
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* @param {*} [thisArg] - execution context
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* @returns {number} maximum value
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*
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* @example
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* var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];
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*
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* function accessor( v ) {
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* return v * 2.0;
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* }
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*
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* var v = maxBy( x.length, x, 1, 0, accessor );
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* // returns 8.0
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*/
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function maxBy( N, x, stride, offset, clbk, thisArg ) {
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var max;
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var ix;
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var v;
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var i;
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if ( N <= 0 ) {
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return NaN;
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}
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if ( N === 1 || stride === 0 ) {
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v = clbk.call( thisArg, x[ 0 ], 0, 0, x );
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if ( v === void 0 ) {
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return NaN;
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}
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return v;
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}
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ix = offset;
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for ( i = 0; i < N; i++ ) {
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max = clbk.call( thisArg, x[ ix ], i, ix, x );
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if ( max !== void 0 ) {
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break;
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}
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ix += stride;
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}
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if ( i === N ) {
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return NaN;
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}
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i += 1;
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for ( i; i < N; i++ ) {
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ix += stride;
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v = clbk.call( thisArg, x[ ix ], i, ix, x );
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if ( v === void 0 ) {
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continue;
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}
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if ( isnan( v ) ) {
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return v;
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}
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if ( v > max || ( v === max && isPositiveZero( v ) ) ) {
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max = v;
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}
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}
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return max;
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}
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// EXPORTS //
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module.exports = maxBy;
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